1. Field of the art
The present invention is concerned with piperidine derivatives of a novel structure.
More particularly, the present invention relates to 2,2,6,6-tetraalkylpiperidine derivatives which are useful as photostabilizers/lightstabilizer or as intermediates therefor and are also usable as intermediates for pharmaceuticals and agricultural chemicals.
2. Related art
It has heretofore been known in the art that chemical compounds having a 2,2,6,6-tetraalkylpiperidine structure, viz. what is called hindered amine structure, have capability of capturing radicals at a high level, whereby these compounds have been used as photostabilizers for various organic materials, particularly resins.
The most typical hindered amine compounds having the photostabilizing capability may be 2,2,6,6-tetramethyl-4-piperidinol of a formula (1) which is often and hereinbelow abbreviated as TMPNL: ##STR2##
Most commercially available photostabilizers are derivatives of TMPNL in that it is used as an intermediate and is processed to have a higher molecular weight by, e.g. condensation with a polybasic carboxylic acid. For instance, as shown in Y. Nakahara et al: RECENT DEVELOPMENT IN ADDITIVES FOR HIGH POLYMERS (in Japanese), C.M.C. Corp. 1988, bis(2,2,6,6-tetramethyl-4-piperidyl)sebacate which is a representative photostabilizer known to have high photostabilizing capability to a lot of resins and hereinbelow referred to as LS770 is an ester of TMPNL with sebacic acid of a formula: ##STR3##
While the TMPNL derivatives representable by LS770 have high photostabilizing capability, they may have disadvantages such that they easily breed out from resin compositions to which they have been added whereby it may be difficult to use them in resin compositions for use as thin articles such as film, and even when they are used in resin compositions for use as thick articles, the surface of the articles may be deteriorated by the breeding out whereby coatability of the articles is deteriorated.
In order to solve these problems, various piperidine derivatives have heretofore been synthesized, such as a piperidinone derivative disclosed in Japanese Patent Publication No. 42987/1979 having a formula: ##STR4## wherein R.sup.0 is a phenyl group or a 2-furyl group.
The compound of formula (3) may have some disadvantages, as long as the present inventors know, such that it may be difficult to process it to have a higher molecular weight and the resin compositions having the compound added as a photostabilizer may be discolored when the compositions are fabricated.